this animation shows brain development from conception through birth in the first four weeks after conception neural tissue known as the neural plate forms in the outermost layer of embryonic cells the neural plate folds to form the neural groove then curls to form the neural tube this tube differentiates into the forebrain the midbrain the hind brain and the spinal cord the forebrain will develop to the cerebral cortex which translates sensory stimulation it also controls complex behaviors thoughts memories and problem-solving the midbrain will develop into a neural relay station for sending information from the body to various sites in the brain the hind brain will control the most basic physiological processes such as breathing and heart rate the spinal cord is the pathway for conveying information between the brain and the rest of the body between weeks four and eight the embryo grows rapidly and the face becomes recognizably human the eyes on the side of the head begin to migrate forward and two distinct hemispheres of the cerebral cortex emerge between weeks 8 and 26 of the fetal stage the cerebral cortex grows to cover the midbrain by week 28 a major structural change begins the cortex expands greatly in surface area and becomes wrinkled and folded inside of the skull beginning at week 28 and continuing through week 40 the brain surface fills with hills and valleys called gyri and sulci these cerebral folds and wrinkles help to create a vast neural network which allows the brain to become a highly flexible yet precise control center and processor of information by week eight the structures of the brain are already in place but the amount of brain tissue is rapidly increasing as many new nerve cells are formed the formation of new cells is known as neurogenesis or neural migration during neurogenesis new nerve cells migrate from the innermost layers of tissue outward like gymnasts climbing ropes the young cells are guided to their final destination by fibers from another type of cell the glial cell glial cells form the underlying structure of the nervous system although earlier formed cells rest closer to where they originated later form cells move further away from their starting point in this way the brain grows adding layers to itself like the skins of an onion once each nerve cell reaches its destination it begins to acquire characteristics specific to that area of the brain at this point each nerve cell sprouts the extensions it needs to communicate with other neurons there are two types of extensions dendrites and axons dendrites look like a network of antennas and receive incoming signals an axon is a single larger extension which carries outgoing signals to other neurons synaptogenesis is the process in which synapses proliferate in the brain a synapse is a tiny gap between the dendrites of one neuron and the axon terminal of the next it's the point of communication between two neurons so many new axons and dendrites form during the process that it's sometimes called exuberant synaptogenesis this cell growth process continues into a new borns first year of life you for an information signal or impulse to move from the axon of one neuron to the dent rights of another it must cross the synaptic gap in this animation an impulse looks like a green ball of light when an impulse reaches the end of an axon a chemical called a neurotransmitter is released in this animation neurotransmitters look like red balls of light neurotransmitters allow an impulse to cross from the axon of one neuron across the synapse and on to a receiving dent right on another neuron to create a more efficient and rapidly working brain some of the newly-formed synapses are eventually removed synaptic pruning occurs during the fetal period infancy childhood and adolescence it's believed that pruning is a way in which the brain becomes customized to an individual's nervous system as a response to that individuals unique experiences